The present invention relates to a tricycle in which a steering shaft leading to a steering handlebar is turnably carried on a handle post provided at a front end of a vehicle body frame assembly; left and right front forks for rotatably supporting left and right front wheels respectively are disposed on laterally opposite sides of the handle post to extend upwards and downwards and are turnably carried on left and right side posts supported on the handle post; the steering shaft is connected to the front forks to enable the steering of the front wheels in response to the turning operation of the steering shaft; an upper link connected at opposite ends thereof to the left and right side posts and a lower link disposed below the upper link and connected at opposite ends thereof to the left and right side posts are turnably connected at central portions thereof to the handle post; and a driven wheel is supported at a rear portion of the vehicle body frame assembly.
The terms xe2x80x9cleftxe2x80x9dand xe2x80x9crightxe2x80x9dused in this specification indicate left and right in a state in which the tricycle is turned forwards in a traveling direction.
Such a tricycle is already known from WO99/61304. In this tricycle, the steering travelability is enhanced by enabling a bank-traveling of the tricycle in an attitude inclined either leftwards or rightwards.
It should be noted here that in the conventionally known tricycle, left and right side posts are disposed on laterally opposite sides of a handle post to extend vertically in parallel to each other, and left and right front wheels rotatably carried on left and right front forks turnably supported on the side posts are in contact with road surface at right angles during straight traveling of the tricycle. However, during steep-bank traveling of the tricycle with the vehicle body frame assembly inclined largely either leftwards or rightwards, outer one of the left and right front wheels may be floated from the road surface, and the inner front wheel and the rear wheel may be in states in which they are in contact with the road surface, in some cases. In the conventionally known tricycle, the inner front wheel is brought into contact with the road surface in an inclined attitude, and during steep-bank traveling of the tricycle inclined largely, there is a possibility that the bracing of the tricycle by the front wheel which is in contact with the road surface is insufficient.
The present invention has been accomplished with such circumstances in view, and it is an object of the present invention to provide a tricycle constructed so that the tricycle can be braced sufficiently by an inner front wheel during bank-traveling thereof.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a tricycle in which a steering shaft leading to a steering handlebar is turnably carried on a handle post provided at a front end of a vehicle body frame assembly; left and right front forks for rotatably supporting left and right front wheels respectively are disposed on laterally opposite sides of the handle post to extend upwards and downwards and are turnably carried on left and right side posts supported on the handle post; the steering shaft is connected to the front forks to enable the steering of the front wheels in response to the turning operation of the steering shaft; an upper link connected at opposite ends thereof to the left and right side posts and a lower link disposed below the upper link and connected at opposite ends thereof to the left and right side posts are turnably connected at central portions thereof to the handle post; and a driven wheel is supported at a rear portion of the vehicle body frame assembly, characterized in that the left and right side posts are disposed in an inclined state, so that the distance between both of the side posts is decreased toward upper portions thereof.
With such arrangement of the first feature, the left and right side posts are inclined so that the distance between both of the side posts is decreased toward their upper portions. Therefore, during steep-bank traveling of the tricycle with the vehicle body frame assembly inclined largely either leftwards or rightwards, one of the left and right side posts assumes an attitude vertical or near vertical to a road surface, and the front wheel rotatably carried on the front fork supported by the one side post, i.e., the inner front wheel is in contact with the road surface in an attitude vertical or near vertical to the road surface. Thus, the tricycle can be braced sufficiently by the inner front wheel during the bank-traveling thereof.
According to a second aspect and feature of the present invention, in addition to the arrangement of the first feature, the lengths of the upper and lower links are set to be equal to each other, and the amount of protrusion, from the left and right side posts, of lower brackets secured to the left and right side posts in order to connect the opposite ends of the lower link is set to be larger than the amount of protrusion, from the left and right side posts, of upper brackets secured to the left and right side posts in order to connect the opposite ends of the upper link. With such arrangement, regardless of the inclination of the left and right side posts, the upper and lower links as framing members forming the substantially parallel link mechanism can be formed in common with each other.
Further, according to a third aspect and feature of the present invention, in addition to the first or second feature, an upright attitude-maintaining means for exhibiting a spring force for biasing the handle post to the upright attitude thereof by the either leftward or rightward tilting of the handle post is provided between one of the upper and lower links and the handle post on either one of the left or right of the handle post. With such arrangement, the spring force for biasing the handle post to its upright attitude can be applied to the handle post during either leftward or rightward tilting of the handle post by the single upright attitude-maintaining means disposed on the either left or right of the handle post, leading to a simplified construction.